Heavy metal precipitant with chelating function as well as preparation method and application of heavy metal precipitant

Abstract

The invention belongs to the technical field of heavy metal wastewater treatment, and particularly relates to a heavy metal precipitant with a chelating function and a preparation method and application thereof. The preparation method comprises the following steps: adding polyacrylonitrile into a hydroxylamine reagent, adjusting the pH value to 6-7, and carrying out an amidoximation reaction to obtain amidoximated polyacrylonitrile; washing the amidoximated polyacrylonitrile, adding the washed amidoximated polyacrylonitrile into an aqueous solution containing an activator, adjusting the pH value to 5-8, and carrying out an activation reaction to obtain an intermediate product; and adding the intermediate product into an aqueous solution containing a dispersant, a surfactant and chloroacetic acid, adjusting the pH value to 6-8, and carrying out nucleophilic substitution reaction to obtain the product. The heavy metal precipitator is large in adsorption capacity and high in adsorption speed, has an excellent chelating function on ultralow-concentration divalent heavy metal ions, can be used for purification and recovery of precious metal in the fields of hydrometallurgy, environmental protection and the like, and can also be used for separation and recovery of rare elements such as uranium, gallium and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of heavy metal wastewater treatment, and specifically relates to a heavy metal precipitant with a chelating function and a preparation method and application thereof. Background Art

[0002] Heavy metal wastewater is generated in industries such as electroplating, electronics, petrochemicals, metal processing, waste incineration, and power plant flue gas washing. Currently, chemical precipitation is mostly used to treat the heavy metals in wastewater. However, due to the different optimal pH values ​​for different heavy metal ions to generate hydroxide precipitation, the treatment effect is not ideal and there are problems such as secondary pollution. Summary of the invention

[0003] The purpose of the present invention is to provide a heavy metal precipitant with chelating function and a preparation method and application thereof, which has the advantages of fast adsorption speed, large adsorption capacity, high strength and easy separation, especially has a good precipitation and removal effect on low-concentration heavy metal ions. At the same time, the preparation method is simple and easy to industrialize. It is suitable for the treatment of heavy metal ion wastewater in the fields of electroplating, petrochemical, environmental protection, etc., and has broad application prospects.

[0004] Specifically, the present invention provides the following technical solutions:

[0005] A method for preparing a heavy metal precipitant with chelating function comprises the following steps:

[0006] 1) adding polyacrylonitrile (PAN) to a hydroxylamine reagent, adjusting the pH value to 6-7, and performing an amine oximation (AO) reaction to obtain amine oximation polyacrylonitrile (PAN-AO);

[0007] 2) washing the amine-oximated polyacrylonitrile, and then adding it to an aqueous solution containing an activator, adjusting the pH value to 5-8, and performing an activation reaction to obtain an intermediate product (h-PAN-AO);

[0008] The activator is selected from at least one of methanol, ethanol, acetone, dichloromethane, pyridine and petroleum ether;

[0009] 3) adding the intermediate product to an aqueous solution containing a dispersant, a surfactant and chloroacetic acid, adjusting the pH value to 6-8, and performing a nucleophilic substitution reaction to obtain a heavy metal precipitant (PAN-AO-DAA) with a chelating function.

[0010] The preparation method provided by the present invention creatively introduces an activation reaction process and prepares a highly active polyamidoximine intermediate h-PAN-AO material. Compared with PAN-AO, h-PAN-AO has higher reaction activity, and its functional groups are all exposed on the outside of the powder matrix, which reduces the attack reaction of chemical reagents into the inside of the matrix, thereby ensuring that the self-strength of the matrix material is not destroyed and improving the yield of the PAN-AO-DAA precipitant.

[0011] In the preparation method provided by the present invention, the amidoximation reaction in step 1 refers to converting the nitrile amidoxime in polyacrylonitrile into amidoxime groups; during step 1, side reactions occur between some amidoxime groups, and the activation reaction in step 2 mainly converts the amidoxime groups that undergo side reactions, thereby improving the reaction efficiency of nucleophilic substitution in step 3; the amine group in the amidoxime group has nucleophilicity, and it will attack the carbon atom of chloroacetic acid and replace the chlorine atom, and in step 3, chloroacetic acid is grafted onto the surface of the material through a nucleophilic substitution reaction.

[0012] The heavy metal precipitant (PAN-AO-DAA) prepared by the present invention through the above-mentioned amidoximation, activation and nucleophilic substitution reaction process is in the form of solid particles. The sodium imidediacetic acid type structure contained on the surface can react chemically with low-concentration heavy metal ions such as copper and nickel, and has the characteristics of fast adsorption speed, large adsorption capacity, high strength, easy separation, etc., especially has a good precipitation and removal effect on low-concentration heavy metal ions, and has broad application prospects.

[0013] Preferably, in step 1), the polyacrylonitrile is in powder or granular form, and has a molecular weight of 30,000-100,000 (number average molecular weight measured by gel permeation chromatography GPC). The present invention has clear requirements on the molecular weight of the polyacrylonitrile raw material. Studies have found that polyacrylonitrile particles with a molecular weight of 30,000-100,000 have good stability in heavy metal adsorption and precipitation applications after modification. If the molecular weight is too low, it is easy to lose mass, and if the molecular weight is too high, the internal group reaction is incomplete.

[0014] Preferably, in step 1), the density of the polyacrylonitrile is 1.1-1.2 g / cm 3 .

[0015] Preferably, in step 1), the hydroxylamine reagent is at least one of hydroxylamine hydrochloride and hydroxylamine sulfate, and the mass ratio of the hydroxylamine reagent to polyacrylonitrile is 1:1-3:1.

[0016] Preferably, in step 1), the temperature of the amine oximation reaction is 60-90° C. and the time is 0.5-2 h.

[0017] Preferably, in step 2), the volume fraction of the activator in the aqueous solution containing the activator is 0.2%-5%.

[0018] Preferably, in step 2), based on the usage of 1 g of the amine oximated polyacrylonitrile (PAN-AO), the usage of the aqueous solution containing the activator is 25-100 ml.

[0019] Preferably, in step 2), when the activator is selected from at least one of methanol, ethanol and acetone, the pH value is adjusted to 5-7;

[0020] When the activator is selected from at least one of dichloromethane, pyridine and petroleum ether, the pH value is adjusted to 7-8. Studies have found that for different activators, adjusting the solution to the above specific pH range can result in higher nucleophilic substitution reaction activity of the prepared h-PAN-AO.

[0021] Preferably, in step 2), the activation reaction is carried out at a temperature of 25-60° C. and for a time of 0.5-2 h.

[0022] Preferably, in step 3), the dispersant is selected from at least one of gelatin, carboxymethyl cellulose, polyvinyl alcohol and sodium lignin sulfonate;

[0023] And / or, the surfactant is a nonionic surfactant; more preferably at least one of fatty alcohol polyoxyethylene ether (AEO-9) and fatty acid polyoxyethylene ester.

[0024] Preferably, in step 3), based on 1 g of the intermediate product (h-PAN-AO), the amount of chloroacetic acid used is 2 to 3 g;

[0025] and / or, based on 1 g of the intermediate product (h-PAN-AO), the amount of the dispersant is 2 to 3 g;

[0026] And / or, based on the usage of the intermediate product (h-PAN-AO) as 1 g, the usage of the surfactant is 0.5-2 g.

[0027] Preferably, in step 3), the nucleophilic substitution reaction is specifically: first reacting at 50-70° C. for 1.5-2.5 h, and then reacting at 80-90° C. for 2.5-3.5 h. The nucleophilic substitution reaction of the present invention adopts the above-mentioned specific temperature program for reaction, which is mainly the reaction condition explored by the inventor according to the reaction mechanism, otherwise there is the disadvantage that the reaction does not proceed or the reaction is not complete.

[0028] Preferably, in step 1), sodium bicarbonate is used to adjust the pH value;

[0029] In step 2), sodium bicarbonate is used to adjust the pH value;

[0030] In step 3), a sodium carbonate solution with a mass fraction of 1% to 5% is used to adjust the pH value. Adjusting the pH of the solution is the key to controlling the group modification and reaction, otherwise it will cause no reaction or side reaction or incomplete reaction.

[0031] Further preferably, in step 3), during the nucleophilic substitution reaction, the pH of the reaction system is controlled to be 6-8 by adding a sodium carbonate solution with a mass fraction of 1%-5%.

[0032] The present invention also provides a heavy metal precipitant with chelating function, which is prepared by the above preparation method.

[0033] The present invention also provides the use of the heavy metal precipitant with chelating function or the heavy metal precipitant with chelating function prepared by the above preparation method in the treatment of heavy metal wastewater containing at least one of copper, lead, zinc and nickel.

[0034] The present invention also provides the use of the heavy metal precipitant with chelating function or the heavy metal precipitant with chelating function prepared by the preparation method in the separation and recovery of rare elements (such as uranium and gallium).

[0035] The beneficial effects of the present invention are at least:

[0036] 1) The preparation method of the heavy metal precipitant with chelating function provided by the present invention creatively introduces an activation reaction process and prepares a highly active polyamidoximine intermediate h-PAN-AO material. Compared with PAN-AO, h-PAN-AO has higher reactivity, and its functional groups are exposed on the outside of the powder matrix, which reduces the attack reaction of chemical reagents into the matrix, thereby ensuring that the strength of the matrix material itself is not damaged and improving the yield of the PAN-AO-DAA precipitant;

[0037] 2) The preparation method of the heavy metal precipitant with chelating function provided by the present invention is a heavy metal precipitant (PAN-AO-DAA) in the form of solid particles through the process of amine oximation, activation and nucleophilic substitution reaction. The sodium imide diacetate type structure contained on the surface can react chemically with heavy metal ions such as copper and nickel. It has the characteristics of fast adsorption speed, large adsorption capacity, high strength, easy separation, etc., especially has a good precipitation and removal effect on low-concentration heavy metal ions, and has broad application prospects;

[0038] 3) The preparation method of the heavy metal precipitant with chelating function provided by the present invention is simple and easy to industrialize. It is particularly suitable for the treatment of heavy metal wastewater containing low concentrations of copper, lead, zinc or nickel, and can also be used for the separation and recovery of rare elements such as uranium and gallium.

[0039] 4) The method for preparing the heavy metal precipitant with chelating function provided by the present invention adjusts the solution to a specific pH range for different activators, so that the nucleophilic substitution reaction activity of the prepared h-PAN-AO is higher. DETAILED DESCRIPTION

[0040] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention is described clearly and completely below. The following embodiments are used to illustrate the present invention, but are not used to limit the scope of the present invention. If no specific technology or conditions are specified in the embodiments, the technology or conditions described in the literature in the field or the product instructions are used.

[0041] The molecular weight of polyacrylonitrile in the examples is the number average molecular weight measured by gel permeation chromatography (GPC).

[0042] In the following examples, information of each reagent used is shown in Table 1.

[0043] Table 1 Information of reagents used in the examples

[0044] Reagents factory Hydroxylamine hydrochloride MacLean's reagent Hydroxylamine sulfate MacLean's reagent Polyvinyl alcohol Aladdin Fatty alcohol polyoxyethylene ether Aladdin gelatin Aladdin Fatty acid polyoxyethylene esters Aladdin Chloroacetic acid MacLean's reagent

[0045] Example 1

[0046] 1) 1g molecular weight is 30000 and density is 1.17g / cm 3 Add the polyacrylonitrile powder to 50 ml of aqueous solution containing 1 g of hydroxylamine hydrochloride, add sodium bicarbonate to adjust the pH value to 6, control the reaction temperature to 60°C, and react for 2 h to obtain PAN-AO;

[0047] 2) After washing with pure water, 1 g of PAN-AO was added to 100 ml of an aqueous solution of 0.2% petroleum ether, sodium bicarbonate was added to adjust the pH value to 8, the reaction temperature was controlled to 25° C. and the reaction was carried out for 0.5 h to obtain h-PAN-AO;

[0048] 3) Add 1 g h-PAN-AO to 100 ml of a mixed aqueous solution containing 2 g polyvinyl alcohol, 0.5 g fatty alcohol polyoxyethylene ether (AEO-9) and 2 g chloroacetic acid, adjust the pH value to 6.5 with 1% sodium carbonate solution, first react at 60°C for 2 h, then increase the temperature to 80°C and react for 3 h while monitoring the pH at any time and adding sodium carbonate solution to maintain the pH of the system at 6.5. After the reaction is completed, filter and wash to obtain PAN-AO-DAA particles.

[0049] Weigh 0.1g PAN-AO-DAA and put it into 20ml copper-containing solution with an initial concentration of 10mg / L (copper exists in the form of divalent copper ions), adjust the pH value to 5.2, and oscillate and adsorb for 1h. The copper content in the solution is lower than the instrument detection limit of 0.05mg / L and is not detected. It can be seen that it has a good treatment effect on low-concentration copper solutions.

[0050] Example 2

[0051] 1) 1g molecular weight is 70000 and density is 1.18g / cm 3 Add the polyacrylonitrile particles into 50 ml of aqueous solution containing 3 g of hydroxylamine sulfate, add sodium bicarbonate to adjust the pH value to 7, control the reaction temperature to 90°C, and react for 0.5 h to obtain PAN-AO;

[0052] 2) After washing, 1 g of PAN-AO was added to 100 ml of an aqueous solution of 1% ethanol by volume, the pH value was adjusted to 6, the reaction temperature was controlled to 60° C. and the reaction was carried out for 2 h to obtain h-PAN-AO;

[0053] 3) Add 1 g h-PAN-AO to 100 ml of a mixed aqueous solution containing 3 g gelatin, 1 g fatty acid polyoxyethylene ester and 3 g chloroacetic acid, adjust the pH value to 8 with 5% sodium carbonate solution, first react at 60°C for 2 h, then increase the temperature to 80°C and react for 3 h while monitoring the pH at any time and adding sodium carbonate solution to maintain the system pH at 8. After the reaction is completed, filter and wash to obtain PAN-AO-DAA particles.

[0054] Weigh 0.1g PAN-AO-DAA and put it into 20ml nickel-containing solution with an initial concentration of 10mg / L (nickel exists in the form of divalent nickel ions), adjust the pH value to 4.5, and oscillate and adsorb for 1h. The nickel content in the solution is lower than the detection limit of the instrument and is not detected. It can be seen that it has a good treatment effect on low-concentration nickel solutions.

[0055] Comparative Example 1

[0056] Compared with Example 1, the only difference is that the activation reaction in step 2) is not carried out, and PAN-AO is directly used in step 3).

[0057] 0.1 g of the precipitant prepared in Comparative Example 1 was weighed and put into 20 ml of a copper-containing solution with an initial concentration of 10 mg / L. The pH value was adjusted to 5.2, and oscillation adsorption was performed for 1 hour. The copper content in the solution was detected to be 4.2 mg / L.

[0058] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a heavy metal precipitant with chelating function, characterized in that: The following steps are involved: 1) adding polyacrylonitrile to a hydroxylamine reagent, adjusting the pH value to 6-7, and performing an oxime reaction to obtain oxime-modified polyacrylonitrile; 2) washing the amine-oximated polyacrylonitrile, and then adding it to an aqueous solution containing an activator, adjusting the pH value to 5-8, and performing an activation reaction to obtain an intermediate product; The activator is selected from at least one of methanol, ethanol, acetone, dichloromethane, pyridine and petroleum ether; 3) adding the intermediate product to an aqueous solution containing a dispersant, a surfactant and chloroacetic acid, adjusting the pH value to 6-8, and performing a nucleophilic substitution reaction to obtain a heavy metal precipitant with a chelating function.

2. The preparation method according to claim 1, characterized in that: In step 1), the polyacrylonitrile is in powder or granular form, and has a molecular weight of 30,000-100,000.

3. The preparation method according to claim 1 or 2, characterized in that: In step 1), the hydroxylamine reagent is at least one of hydroxylamine hydrochloride and hydroxylamine sulfate, and the mass ratio of the hydroxylamine reagent to polyacrylonitrile is 1:1-3:

1.

4. The preparation method according to claim 1 or 2, characterized in that: In step 2), the volume fraction of the activator in the aqueous solution containing the activator is 0.2%-5%.

5. The preparation method according to claim 1 or 2, characterized in that: In step 2), when the activator is selected from at least one of methanol, ethanol and acetone, the pH value is adjusted to 5-7; When the activator is selected from at least one of dichloromethane, pyridine and petroleum ether, the pH value is adjusted to 7-8.

6. The preparation method according to claim 1 or 2, characterized in that: In step 3), the dispersant is selected from at least one of gelatin, carboxymethyl cellulose, polyvinyl alcohol and sodium lignin sulfonate; And / or, the surfactant is a nonionic surfactant; preferably at least one of fatty alcohol polyoxyethylene ether and fatty acid polyoxyethylene ester.

7. The preparation method according to claim 1 or 2, characterized in that: In step 3), based on the amount of the intermediate product (h-PAN-AO) being 1 g, the amount of chloroacetic acid being 2 to 3 g; and / or, based on 1 g of the intermediate product (h-PAN-AO), the amount of the dispersant is 2 to 3 g; And / or, based on the usage of the intermediate product (h-PAN-AO) as 1 g, the usage of the surfactant is 0.5-2 g.

8. A heavy metal precipitant with chelating function, characterized in that: It is prepared by the preparation method according to any one of claims 1 to 7.

9. Use of the heavy metal precipitant prepared by the preparation method according to any one of claims 1 to 7 or the heavy metal precipitant according to claim 8 in the treatment of heavy metal wastewater containing at least one of copper, lead, zinc and nickel.

10. Use of the heavy metal precipitant prepared by the preparation method according to any one of claims 1 to 7 or the heavy metal precipitant according to claim 8 in the separation and recovery of rare elements.